Polyethylene is a polymer chain formed from the polymerization of ethylene monomers. In its simplest form, polyethylene can be represented by the following general formula: 
As shown, the polyethylene constitutes a linear polyethylene because it has little to no polymer side chains that offshoot from the main polymer chain. Polyethylene with this structure is called high density polyethylene (HDPE). During polymerization of polyethylene, however, branching can occur where other polyethylene side chains are formed and branch off from the main polymer chain to form a branched polymer molecule. Typically, short chain branches (usually three to ten carbons long) are formed by adding an alpha-olefin comonomer. Adding short chain branches lowers the density by disrupting the crystallization process. In large enough quantities (densities lower than 0.940 g/cc) this forms a class of polyethylene called linear low density polyethylene (LLDPE). The third general class of polyethylene is low density polyethylene (LDPE). It is produced by a high-temperature and high pressure, radical-initiated polymerization process which forms a highly branched polymer with approximately 60 branch points per 1000 carbon atoms.
Polyethylene is used in manufacturing a variety of different products. Among these include films or sheet-like materials used for product packaging, merchandise bags, trash and can liners, medical packaging, stretch and shrink wrap, and the like. One common method of forming polyethylene films is through a blown film process. In this process, molten polyethylene is extruded through an annular die to form a vertical column or sleeve. Air is blown through the center of the sleeve to expand the film. Air may also be blown along the exterior of the sleeve to facilitate cooling of the polyethylene. The sleeve is then collapsed and collected on rollers.
In many polyethylene blown film processes, the polyethylene film has a somewhat opaque or hazy appearance. For many applications, this is often a desirable property of the film. The haze or clarity of the film and its causes are the subject of much study. It is believed that both surface properties of the film, as well as bulk properties of the resin, contribute to this hazy appearance. There are many theories, however, as to the physics and mechanics that contribute to this phenomenon.